Ted Ernst reminds me of a reason not to have a valve nut in place at all.
In 1987 a few college classmates and I were rolling down PCH (Pacific Coast Highway) at about Will Rogers State Beach on a Sunday, lots of traffic, a guy in a car, Ford Fairmont with the big oversize 5 mph bumpers decided to gutterball it to get ahead right in front of me, I turned almost enough but his rear bumper caught my skewer, I got bounced, from a hard right turn to a crossed up rear wheel knocked to the far right to my line of travel, when my tire landed it grabbed and rolled, and of course blew as the valve did not make a clean exit from the rim, but fortunately it did leave, I was now on a bare rim. Everyone behind thought I was going down hard and fast, but I hoped I could load the front brake, and kick the wheel back underneath me. Fortunately I did and rode it out, tossed the tire and rode home on the spare. I really don't like falling, I consider myself allergic to it, and avoid it at all costs. The Ford saw all this excitement behind it I guess as they tore out of there in a big way.
John Jorgensen
Torrance Ca USA
South of Malibu California.